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te: Thu, 17 Apr 2003 11:25:26 -0700 From: "Jim" Subject: [SDL] Frame buffer patches... Would seem that GCC 3.2.2 promotes all signed values to unsigned if any single vlaue is unsigned in an expression... for instance when calculating an elo touch position....evertyhign is an (int) except for cach_vinfo.xres which is unsigned. THerefore if y ou reverse the SDL_ELO_MIN_X and SDL_ELO_MAX_X values the resulging negative value pegs the expression to it's max. Attached it the accumu lated patch to typecast the unsigned values to (int) - *dx = (cache_vinfo.xres - (cache_vinfo.xres * (input_x - ELO_MIN_X)) / width); + *dx = ((int)cache_vinfo.xres - ((int)cache_vinfo.xres * (input_x - ELO_MIN_X)) / width); and also to provide quite failure to operations which have the screen currently locked... The touch screen I'm using the original values were exactly opposite of any position I touched on the screen - evaluating the math the expr ession SHOULD have handled reversing the min and max values - and after casting the unsigned .xres and .yres to a signed int - worked well. .. Jim
author Sam Lantinga <slouken@libsdl.org>
date Tue, 24 Jan 2006 06:36:43 +0000
parents 355632dca928
children
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<HTML
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><TITLE
>SDL_AudioCVT</TITLE
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><H1
><A
NAME="SDLAUDIOCVT"
></A
>SDL_AudioCVT</H1
><DIV
CLASS="REFNAMEDIV"
><A
NAME="AEN6884"
></A
><H2
>Name</H2
>SDL_AudioCVT&nbsp;--&nbsp;Audio Conversion Structure</DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN6887"
></A
><H2
>Structure Definition</H2
><PRE
CLASS="PROGRAMLISTING"
>typedef struct{
  int needed;
  Uint16 src_format;
  Uint16 dest_format;
  double rate_incr;
  Uint8 *buf;
  int len;
  int len_cvt;
  int len_mult;
  double len_ratio;
  void (*filters[10])(struct SDL_AudioCVT *cvt, Uint16 format);
  int filter_index;
} SDL_AudioCVT;</PRE
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN6890"
></A
><H2
>Structure Data</H2
><DIV
CLASS="INFORMALTABLE"
><A
NAME="AEN6892"
></A
><P
></P
><TABLE
BORDER="0"
CLASS="CALSTABLE"
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>needed</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Set to one if the conversion is possible</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>src_format</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Audio format of the source</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>dest_format</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Audio format of the destination</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>rate_incr</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Rate conversion increment</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Audio buffer</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Length of the original audio buffer in bytes</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>len_cvt</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Length of converted audio buffer in bytes (calculated)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> must be <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
> bytes in size(calculated)</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>len_ratio</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Final audio size is <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_ratio</I
></TT
></TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>filters[10](..)</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Pointers to functions needed for this conversion</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="TOP"
><TT
CLASS="STRUCTFIELD"
><I
>filter_index</I
></TT
></TD
><TD
ALIGN="LEFT"
VALIGN="TOP"
>Current conversion function</TD
></TR
></TBODY
></TABLE
><P
></P
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN6944"
></A
><H2
>Description</H2
><P
>The <SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
> is used to convert audio data between different formats. A <SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
> structure is created with the <A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
> function, while the actual conversion is done by the <A
HREF="sdlconvertaudio.html"
><TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
></A
> function.</P
><P
>Many of the fields in the <SPAN
CLASS="STRUCTNAME"
>SDL_AudioCVT</SPAN
> structure should be considered private and their function will not be discussed here.</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
><SPAN
CLASS="TYPE"
>Uint8 *</SPAN
><TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
></DT
><DD
><P
>This points to the audio data that will be used in the conversion. It is both the source and the destination, which means the converted audio data overwrites the original data. It also means that the converted data may be larger than the original data (if you were converting from 8-bit to 16-bit, for instance), so you must ensure <TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> is large enough. See below.</P
></DD
><DT
><SPAN
CLASS="TYPE"
>int</SPAN
> <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
></DT
><DD
><P
>This is the length of the original audio data in bytes.</P
></DD
><DT
><SPAN
CLASS="TYPE"
>int</SPAN
> <TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
></DT
><DD
><P
>As explained above, the audio buffer needs to be big enough to store the converted data, which may be bigger than the original audio data. The length of <TT
CLASS="STRUCTFIELD"
><I
>buf</I
></TT
> should be <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
>.</P
></DD
><DT
><SPAN
CLASS="TYPE"
>double</SPAN
> <TT
CLASS="STRUCTFIELD"
><I
>len_ratio</I
></TT
></DT
><DD
><P
>When you have finished converting your audio data, you need to know how much of your audio buffer is valid. <TT
CLASS="STRUCTFIELD"
><I
>len</I
></TT
>*<TT
CLASS="STRUCTFIELD"
><I
>len_ratio</I
></TT
> is the size of the converted audio data in bytes. This is very similar to <TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
>, however when the convert audio data is shorter than the original <TT
CLASS="STRUCTFIELD"
><I
>len_mult</I
></TT
> would be 1. <TT
CLASS="STRUCTFIELD"
><I
>len_ratio</I
></TT
>, on the other hand, would be a fractional number between 0 and 1.</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="REFSECT1"
><A
NAME="AEN6989"
></A
><H2
>See Also</H2
><P
><A
HREF="sdlbuildaudiocvt.html"
><TT
CLASS="FUNCTION"
>SDL_BuildAudioCVT</TT
></A
>,
<A
HREF="sdlconvertaudio.html"
><TT
CLASS="FUNCTION"
>SDL_ConvertAudio</TT
></A
>,
<A
HREF="sdlaudiospec.html"
><SPAN
CLASS="STRUCTNAME"
>SDL_AudioSpec</SPAN
></A
></P
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